1. Technical Field
One or more embodiments of the present invention relate to an electronic component mounting device in which an electronic component is mounted in a housing having an electromagnetic shielding function, and a method for manufacturing the same.
2. Background Art
An electronic component mounting device in which various types of electronic components are mounted in a housing is conventionally known. In such device, a technique of providing an electromagnetic shielding function to the housing or the like to suppress the electromagnetic noise from entering inside the device from the outside and to suppress the leakage of the electromagnetic noise from the inside to the outside is known.
In recent years, issues arising from the electromagnetic noise are increasing with miniaturization and higher speed operation of the electronic device on which the electronic component circuit is mounted. For instance, in an in-vehicle micro-computer or the like, the number of codes of the software exceeds 2 hundred thousand rows and the operation frequency reaches 100 MHz, and hence the false operation of the electronic circuit caused by the electromagnetic noise generated from each electronic component is significant. The electromagnetic resistance characteristic of the semiconductor chip is lowering due to miniaturization, microscopic wiring, and smaller power. Therefore, there is a further need to carry out electromagnetic shielding in order to protect the electronic component from external electromagnetic noise and to suppress the electromagnetic noise from the electronic component from leaking to the outside.
Conventionally, a method of placing a cap made of metal or made of resin performed with metal plating on an electronic component circuit substrate (see patent documents 1, 2), a method of coating an electronic component circuit substrate sealed with mold resin with a metal coating (see patent document 3), or the like is known for the electromagnetic shielding technique.
However, in the case of the method of placing a cap having conductivity on the electronic component circuit substrate as in the former case, the cap and the circuit substrate need to be electrically connected, which complicates the production step and increases the cost. The electromagnetic noise leaking from the gap of the wiring circuit of the circuit substrate and the size of the cap being limited by the shape of the circuit substrate thus limits the degree of freedom of design of the cap.
In the case of coating the electronic component circuit substrate with a metal coating as in the latter case, the resin molding step and the metal coating step such as plating and vapor deposition are required, and hence the material cost and the manufacturing cost increase.
A technique of mounting an electronic component inside a substantially sealed housing and providing the electromagnetic shielding function to the housing is also known (see e.g., patent documents 4, 5). The electronic component mounting device according to such related art example will be described with reference to FIG. 5. FIG. 5 is a schematic cross-sectional view of an electronic component mounting device according to a related art example.
In the electronic component mounting device according to the related art example, the housing is configured by a box body 100 and a flat plate shaped lid member 103, where an electronic component 102 is mounted inside the housing. The box body 100 is formed to a box shape having an opening by performing a sheet metal processing such as bend processing or drawing processing to a conductive metal plate. A wiring circuit 101 is formed on the surface of the bottom of the box body 100, and the electronic component 102 is mounted on such wiring circuit 101. The lid member 103 has a conductive circuit 104 formed on a flat plate shaped substrate made of resin.
The box body 100 and the lid member 103 configured as above are fixed such that the wiring circuit 101 and the conductive circuit 104 are electrically connected, so that the periphery of the electronic component 102 can be electromagnetically shielded.
In the conductive circuit 104 of the lid member 103, the gap between the circuits does not have conductivity and the electromagnetic noise may leak out from such portion. If a multi-layered wiring board is used as a countermeasure, the manufacturing cost increases. Furthermore, the wiring circuit 101 on the box body 100 and the conductive circuit 104 on the lid member 103 need to be electrically conducted and connected, and the productivity lowers due to the alignment step of the circuits, the partial supply step of a conductive adhesive, and a heating and curing step. Furthermore, the depth 110 needs to be higher than or equal to the height of the electronic component 102 in order to completely accommodate the electronic component 102 inside the box body 100. Therefore, the material and the processing shape to use are limited to ensure the bending amount, the drawing processing amount of the metal plate by the necessary amount in order to obtain the box body 100 through sheet metal processing. Moreover, the deformation stress involved when the flat plate shaped lid member 103 expands or contracts due to change in the surrounding environmental temperature or the like concentrates at a joining portion 120 of the lid member 103 and the box body 100. Therefore, the joining portion tends to easily strip.    Patent Document 1: Japanese Unexamined Patent Publication No. 08-15236    Patent Document 2: Japanese Unexamined Patent Publication No. 2008-67383    Patent Document 3: Japanese Unexamined Patent Publication No. 09-97854    Patent Document 4: Japanese Unexamined Patent Publication No. 04-6893    Patent Document 5: Japanese Unexamined Patent Publication No. 11-97820    Patent Document 6: Japanese Unexamined Patent Publication No. 2008-199353